Plastic bags used as freezer bags, lunch bags, and storage bags of general utility are often provided with some type of separable fastener formed as molded, interlocking male and female rib and groove elements. U.S. Pat. Nos. 3,338,284; 3,347,298; and Re 28,969 are considered as being representative of the more advanced type of separable fasteners to which the invention relates. For comparison, U.S. Pat. No. 1,959,318 illustrates an earlier construction and also indicates how the art has advanced with improved constructions over the years.
As currently constructed separable fasteners of the type to which the invention relates have two interlocking closure profiles, e.g., rib and groove closure elements formed as protrusions on opposing inner surfaces of the sheet material to be coupled. The closure elements are typically located below or inwardly from the mouth or so-called "flange" portions of the bag. The flanges are gripped to facilitate opening and closing. In order to close a bag having a releasable fastener of this type, the user must first precisely align the two opposing closure elements and then apply pressure along their respective lengths thus forcing the closure elements to engage each other in an interlocking manner. As technology advanced, these closure elements have become increasingly smaller. Accordingly, it has become more difficult for users to manipulate these closure elements into proper alignment.
Throughout the history of the prior art, only the most limited means have been provided to aid the user in placing these closure elements into proper alignment. Currently, except for use of color coding as exemplified in U.S. Pat. No. 4,186,786, no means so far as is known have been provided along the length of the closure elements to facilitate the alignment and subsequent closing operation. U.S. Pat. No. 3,347,298 is noted as teaching a flexible wedge adjacent one side of the groove element. However, such wedge acts as a force-distributing device and is not taught as being useful as a ramp surface. Such aligning aids as are known to exist are provided in the form of localized starting points which are found only at the extreme ends of the closure elements. At these points where the opposing bag walls come together, two unique areas are formed in which the opposing closure elements reside in close proximity to each other. As a result of this close proximity, there exists within these two small areas a natural tendency for the opposing closure elements to be urged into proper alignment. Unfortunately, because these starting areas are so small, many people have difficulty in using them as convenient aids in the proper aligning and subsequent interlocking of the closure elements.
With the foregoing background art in mind, it would be desirable to provide an improved separable fastener construction in which the closure profiles would lend themselves by the manner in which they are formed to ease of alignment and ease of closure. Thus, the obtaining of an improved separable fastener for plastic bags, and the like, becomes the primary object of the present invention. This and other objects will become more apparent as the description proceeds.